You can use tools like [Pingdom and [URL="https://developers.google.com/speed/pagespeed/insights"]Google's PageSpeed](http://tools.pingdom.com/fpt/) to analyse speed of your websites. They also give ways to address the issues that are leading to underperformance and tell you exactly where the issues are.

Looks like you still have some optimising to do in the areas of combining scripts and caching.